General shielded space construction systems which have been conventionally known can be divided into two broad general categories: physical shield system and air curtain. The physical shield system partitions the space with a shield wall such as a plate glass, a partition, and a plastic curtain, and uses a local exhaust device for cleaning the space physically shielded from the outside space with the shield wall. The air curtain system uses a blower fan to produce a forced draft for creating a curtain-like air flow, and by utilizing the curtain-like air flow as a shield plane, prevents the air from being moved from the space on one side of the shield plane to that on the other, thus blocking invasion of foreign matters from the space on the one side of the shield plane to that on the other, and shielding the space on the other side from that on the one side.
Of the two different systems, the physical shield system cannot be adopted for such a facility as that with which a belt conveyor crosses the shield plane, and if it could be used, the shield wall would provide an obstacle for operation, impairing the workability in the shielded space. The shielded space construction system which combines shield walls is not suitable for shielding in a narrow area and a complicated facility.
The air curtain system generates an air flow by applying a pressure to the air, however, a vortex flow is produced behind the air flow. Thus, with the air curtain system, invasion of foreign matters is promoted or a phenomenon of diffusion of foreign matters is caused, resulting from such vortex flow, which makes it difficult to obtain a satisfactory shielding effect.
Thus, the physical shield system provides a poor workability, and the air curtain system gives a poor effect of shield, therefore, the conventional shielded space construction systems present a problem on the workability or shielding effect.
On the other hand, as a device to remove the dirt and dust in the air, a dust collector which generates an ion wind, uses that ion wind to give negative charges to the dust particles in the air, and collects the negatively charged dust particles on the anode is known. With such a dust collector, the reach of the ion wind is as short as 30 cm, the ion wind being supplied only for a local narrow space.
Then, the purpose of the present invention is to provide an air shield plane forming method, a shielded space forming method and device, a local cleaning method and device, and a local cleaning system which are excellent in workability, and yet provide a high shielding effect.